Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 29
Filtrar
Mais filtros










Base de dados
Tipo de estudo
Intervalo de ano de publicação
1.
Food Chem ; 304: 125377, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31476547

RESUMO

We devise a novel colorimetric aptasensor for multiplex antibiotics based on an ss-DNA fragment coordinately controlling gold nanoparticles (AuNPs) aggregation. The multifunctional aptamer (Apt) was elaborately designed to be adsorbed on AuNPs surfaces acting as a binding element for antibiotics and a molecular switch. Chloramphenicol (CAP) and tetracycline (TET) were selected as the model antibiotics. When one kind of antibiotics was added, the specifically recognized fragment of Apt can bind to it and dissociated, and the non-specific one coordinately controls AuNPs aggregation under high-salt conditions. Hence, different color changes of AuNPs solution can be used as the signal readout. The aptasensor exhibited remarkable selectivity and sensitivity for separate detection of TET and CAP, and the detection limits are estimated to be 32.9 and 7.0 nM, respectively. The analysis with the absorption spectroscopy and the smartphone are applied to detect antibiotics in real samples with consistent results and desirable recoveries.

2.
Anal Bioanal Chem ; 2019 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-31641824

RESUMO

A label-free, rapid response colorimetric aptasensor for sensitive detection of chloramphenicol (CAP) was proposed, which was based on the strategy of ssDNA-modified gold nanoparticle (AuNP) aggregation assisted by lanthanum (La3+) ions. The AuNPs generated a color change that could be monitored in the red, green, and blue and analyzed by the smartphone imaging app. La3+, as a trigger agent, strongly combined with the phosphate groups of the surface of ssDNA-AuNPs probe, which helps create AuNP aggregation and the color change of AuNPs from red to blue. On the contrary, when mixing with CAP, the aptamer (Apt) bound to CAP to form a rigid structure of the Apt-CAP complex, and La3+ attached to the phosphate groups of the complex, which prevented the aptamer from binding to the surface of the AuNPs. As a result, the color of the AuNPs changed to violet-red. Finally, UV-vis absorption spectroscopy and the smartphone imaging app were employed to determine CAP with a lower detection limit of 7.65 nM and 5.88 nM, respectively. The proposed strategy featuring high selectivity and strong anti-interference ability for detection of CAP in practical samples was achieved. It is worth mentioning that the simple and portable colorimetric aptasensor will be used for facilitating on-site detection of food samples.

3.
Mikrochim Acta ; 186(7): 467, 2019 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-31240491

RESUMO

A colorimetric assay is described for determination of cytosine-rich ssDNA at physiological pH values. The working principle is based on (a) Ag(I) ion-induced formation of an i-motif structure, and (b) glucose oxidase-controlled growth of gold nanoparticles (AuNPs). The combination between Ag+ and cytosine-rich DNA can modulate the generation of H2O2 resulting from enzyme catalyzed glucose oxidation. Depending on the amount of H2O2 formed, the solution containing the AuNPs will turn red in the presence of cytosine-rich ssDNA but blue in the absence of such DNA if Ag+ is added before the formation of the red AuNPs. Upon addition of C-DNA at different concentrations, the peak shift (Δλ) of the AuNP solution relative to the SPR peak position (560 nm) in the absence of C-DNA is taken as the signal readout. The method shows a good linear response toward C-DNA over the range 10-200 nM with a detection limit of 2.7 nM. It may also be performed visually. The photometric assay is highly sensitive, specific, and rapid. The method is particularly attractive in terms of applications such as in human serum analysis, a colorimetric logic gate, and the calculation of binding constants for the interaction between Ag+ and glucose oxidase (GOx), and between Ag+ and cytosine-rich ssDNAs. Graphical abstract Schematic presentation of colorimetric detection of cytosine (C)-rich ssDNA (C-DNA) based on the modulation of the glucose oxidase (GOx)-catalyzed growth of gold nanoparticles (AuNPs) with Ag+ as the enzyme inhibitor.

4.
Spectrochim Acta A Mol Biomol Spectrosc ; 214: 233-238, 2019 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-30785042

RESUMO

We report a highly sensitive fluorescent probe based on p-dimethylaminobenzoyl derivatives (probe L) for the detection of Cu2+ and Zn2+. In this work, the probe L exhibited a fluorescent turn-on sensing model to Cu2+ and Zn2+ with a distinct fluorescent color change from colorless to green and yellow respectively. Probe L exhibited high selectivity as a fluorescent Cu2+/Zn2+ probe with a limit of detection (LOD) of 45 nM/17 nM. The results of 1H NMR titrations revealed that the response of L to Cu2+ and Zn2+ was triggered by the interaction of the thiophene unit and the metal ion. Furthermore, the fluorescence titrations and Job's plot curves displayed the binding ratio of 1:2 for Cu2+ and 1:1 for Zn2+ metal-L complex formation respectively. Density functional theory calculation also demonstrated the possibility of molecular luminescence and the process of metal-L complex formation. Additionally, fluorescent test strips have been prepared for convenient detection of Cu2+ and Zn2+, which means the convenient and rapid assay in real samples can be achieved.


Assuntos
Cobre/metabolismo , Corantes Fluorescentes , Zinco/metabolismo , Cobre/química , Corantes Fluorescentes/síntese química , Corantes Fluorescentes/química , Corantes Fluorescentes/farmacologia , Células HeLa , Humanos , Limite de Detecção , Espectrometria de Fluorescência , Zinco/química
5.
Anal Chim Acta ; 1034: 144-152, 2018 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-30193628

RESUMO

In our study, the carbon nanodots (CDs) were synthesized by one-step solvothermal method using resorcinol as the only presusor. The obtained CDs contained abundant unsaturated oxygen-containing groups resulting from the surface oxidation. A novel, simple, and real-time fluorescent assay for the detection of water in various organic solvents was thus established by reducing the surface oxidation states. Excellent reversibility can be readily achieved by the external stimulus water and N,N'-dicyclohexylcarbodiimide (DCC). The water-induced sensitive (limit of detection = 0.006%, v/v, in ethanol) and ultrafast (<1 s) response in emission properties was capable of water determination in spirit samples in both solution and solid-state paper test strips.

6.
Spectrochim Acta A Mol Biomol Spectrosc ; 204: 568-575, 2018 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-29975918

RESUMO

In this work, a simple and easily synthesized Schiff-based derivative colorimetric and fluorescent sensor (1), 4-dimethylamino-benzoic acid (2-imidazole formaldehyde)-hydrazide, was obtained for the detection of Cu2+ and S2-. The compound 1 exhibited dual spectral responses to Cu2+, that is, vivid color change and fluorescence enhancement in the presence of Cu2+. The detection limits were valued as 0.46 µM and 15 nM according to absorption and fluorescent response, respectively. Both of them are below the World Health Organization (WHO) guidelines for drinking water (31.5 µM). In addition, the ensemble (1-Cu2+) selectively and sensitively detected a low concentration of S2-. As the addition of S2- instantly removed Cu2+ from the ensemble (1-Cu2+) resulting in a color change from yellow to colorless and a "turn-off" fluorescent response. The detection limit for S2- was estimated as 0.12 µM (from fluorescent method) and 0.68 µM (from absorption method), respectively, each of which was also lower than the maximum allowable level of S2- (15 µM) in drinking water defined by the WHO. The binding process was confirmed via UV-vis absorption, fluorescence measurements, 1H NMR, mass spectroscopy and density functional theory calculation. What's more, successful practical application of test paper is used to inspect the S2- which means the convenient and rapid assay in real samples can be achieved.


Assuntos
Colorimetria/métodos , Cobre/análise , Corantes Fluorescentes/análise , Enxofre/análise , Poluentes Químicos da Água/análise , Água Potável/química , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos Testes
7.
Anal Chem ; 90(11): 7004-7011, 2018 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-29701058

RESUMO

Lanthanide-based luminescent sensors have been widely used for the detection of the anthrax biomarker dipicolinic acid (DPA). However, mainly based on DPA sensitization to the lanthanide core, most of them failed to realize robust detection of DPA in bacterial spores. We proposed a new strategy for reliable detection of DPA by perturbing a tandem energy transfer in heterobinuclear lanthanide coordination polymer nanoparticles simply constructed by two kinds of lanthanide ions, Tb3+ and Eu3+, and guanosine 5'-monophosphate. This smart luminescent probe was demonstrated to exhibit highly sensitive and selective visual luminescence color change upon exposure to DPA, enabling accurate detection of DPA in complex biosystems such as bacterial spores. DPA release from bacterial spores on physiological germination was also successfully monitored in real time by confocal imaging. This probe is thus expected to be a powerful tool for efficient detection of bacterial spores in responding to anthrax threats.

8.
Analyst ; 142(21): 4106-4115, 2017 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-28980671

RESUMO

This work presents a novel and facile strategy for the fabrication of gold-platinum bimetallic nanoclusters (Au-PtNCs) with adjustable Au/Pt molar ratios by a one-pot synthetic route. It was unexpectedly found that the prepared Au-PtNCs with an optimal Au/Pt molar ratio (1 : 1) could exhibit greatly enhanced peroxidase-like catalytic activity and chemical stability toward harsh conditions due to the synergistic effect of the two atoms, in contrast with pure AuNCs. These prominent advantages render Au-PtNCs capable of sensitive and selective colorimetric detection of glucose by means of a NCs-glucose oxidase (GOx) cascade-catalyzed system using 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic substrate. This assay can be used not only for visual detection of glucose by the naked eye but for reliable and convenient quantification in the range from 5 to 55 µM with a detection limit of 2.4 µM. Importantly, to widen the application of point-of-care testing (POCT) of glucose to biomedical diagnosis, an integrated agarose hydrogel-based sensing platform comprising NCs, GOx and TMB was rationally designed. It was demonstrated that this sensing platform could serve as a reagentless and instrument-free platform for direct visualization of glucose with different levels in human serum, as the results were in good accordance with those obtained from a free NC-involved detection system as well as from a commercial blood glucometer.

9.
Methods Appl Fluoresc ; 5(2): 024014, 2017 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-28475492

RESUMO

A new Al3+-specific fluorescent probe NQ was designed and synthesized from 2-hydroxy-1-naphthaldehyde and 2-aminoquinoline. Upon the addition of Al3+, the fluorescent intensity of NQ was significantly enhanced compared with other examined metal ions in aqueous solution. The result of a Job's plot indicated the formation of a 1:1 complex between the probe and Al3+, and the possible binding mode of the system between NQ and Al3+ was clarified by IR analysis and 1H NMR titration. Moreover, other metal ions examined had little effect on the detection of Al3+. The detection limit of NQ for Al3+ detection was 1.98 µM, which is lower than the level (7.4 µM) in drinking water defined by the World Health Organization. In addition, the fluorescent probe NQ could be recyclable simply through treatment with a proper reagent such as F-, and could also be used for the detection of Al3+ in real samples.

10.
Anal Chim Acta ; 967: 64-69, 2017 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-28390487

RESUMO

Glutathione (GSH), the most abundant biothiol in cells, not only plays a pivotal role in protective and detoxifying functions of the cell, but also serves as a very important mediator in many cellular functions. Especially, the difference of GSH level between cancer cells and normal cells is regarded as one of most important physiological parameters for cancer diagnosis. It is thereby extremely necessary to develop a simple, sensitive, and reliable analytical method for detection of GSH in cells. On the basis of the inhibition effect of GSH on the peroxidase-like activity of GSH stabilized gold nanoclusters, here a novel and facile strategy for colorimetric detection of cellular GSH level was well established. In this sensing system, GSH can effectively inhibit the oxidation of peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) to produce a blue colored product. Under the optimized conditions, the absorbance at 652 nm against GSH concentration shows a linear relationship within a range from 2 to 25 µM with detection limit of 420 nM. This excellent property allows our approach to be used to accurately evaluate the cellular GSH levels, and it is revealed that the overall GSH level in cancer cells was much higher than that in normal cells. The presented assay will enable a powerful tool for identifying cancer cells in a simple manner for biomedical diagnosis associated with GSH.


Assuntos
Colorimetria , Glutationa/análise , Ouro , Nanopartículas Metálicas/química , Linhagem Celular Tumoral , Humanos , Limite de Detecção , Neoplasias/diagnóstico , Oxirredução , Peroxidase , Células THP-1
11.
Spectrochim Acta A Mol Biomol Spectrosc ; 173: 264-269, 2017 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-27673495

RESUMO

A new p-dimethylaminobenzamide derivative based compound BDIH has been synthesized. Cu2+ turned on the fluorescence of compound BDIH with a 1:2 binding stoichiometry. The fluorescent color of compound BDIH shows an evident change from colorless to bright blue upon the addition of Cu2+, which could be visibly detected by the naked eye under UV light at 365nm. More importantly, the detection limit was found to be 0.64nM which is far lower than the maximal allowed concentration of the WHO limit (31.5µM) for drinking water. This selective "turn-on" fluorescence sensor was used to identify Cu2+ in living cells using confocal fluorescence microscopy, indicating that compound BDIH has a potential application for selective detection of Cu2+ in organism.


Assuntos
Benzaldeídos/química , Benzoatos/química , Cobre/análise , Hidrazinas/química , Indóis/química , Espectrometria de Fluorescência/métodos , Carcinoma Hepatocelular/química , Linhagem Celular Tumoral , Corantes Fluorescentes/síntese química , Corantes Fluorescentes/química , Humanos , Limite de Detecção , Neoplasias Hepáticas/química , Espectroscopia de Ressonância Magnética , Imagem Molecular/métodos , Sensibilidade e Especificidade , Espectrofotometria Ultravioleta
12.
Talanta ; 140: 143-149, 2015 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-26048836

RESUMO

A new method for real-time detection of carcinoembryonic antigen (CEA) in human serum with high sensitivity and selectivity using surface plasmon resonance (SPR) biosensor was developed. Two kinds of antibodies were used to recognize CEA at different epitopes with high affinity and specificity. Gold nanoparticles (GNPs) modified with streptavidin (SA) were used to further enhance signal specifically via biotin-streptavidin interaction. The binding capacity of the streptavidin-modified gold nanoparticles (SA-GNPs) for ligand biotin was quantified by titration with biotin (5-fluorescein) conjugate to be 10.54 biotin binding sites per 100 nm(2). The developed GNPs enhanced sandwich SPR biosensor successfully fulfilled the sensitive detection of CEA in the range of 1-60 ng/mL with a detection limit of 1.0 ng/mL. Compared to the direct assay format, sandwich format without GNPs and SA-GNPs enhanced sandwich format led to 4.2-fold and 13.8-fold in the sensitivity, respectively. This sensor also showed good selectivity for CEA in the interference study. The results demonstrated that the proposed method could provide a high sensitivity and selectivity in the detection of CEA and offer a promising alternative for cancer biomarker than traditional clinical examinations.


Assuntos
Antígeno Carcinoembrionário/sangue , Ouro/química , Nanopartículas Metálicas/química , Ressonância de Plasmônio de Superfície/métodos , Anticorpos Imobilizados/química , Anticorpos Monoclonais/química , Biotina/química , Humanos , Imunoensaio/métodos , Limite de Detecção , Estreptavidina/química
13.
Talanta ; 132: 619-24, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25476353

RESUMO

Thiocyanate (SCN(-)) is a small anion byproduct of cyanide metabolism. Several methods have been reported to measure SCN(-) above the micromolar level. However, SCN(-) is derived from many sources such as cigarettes, waste water, food and even car exhaust and its effect is cumulative, which makes it necessary to develop methods for the detection of trace SCN(-). In this paper, a simple and ultrasensitive turn-on fluorescence assay of trace SCN(-) is established based on the fluorescence resonance energy transfer (FRET) between gold nanoparticles (AuNPs) and fluorescein. The detection limit is 0.09 nM, to the best of our knowledge, which has been the lowest detection LOD ever without the aid of costly instrumentation. The fluorescence of fluorescein is significantly quenched when it is attached to the surface of AuNPs. Upon the addition of SCN(-), the fluorescence is turned on due to the competition action between SCN(-) and fluorescein towards the surface of AuNPs. Under an optimum pH, AuNPs size and concentration, incubation time, the fluorescence enhancement efficiency [(IF-I0)/I0] displays a linear relationship with the concentration of SCN(-) in the range of 1.0 nM to 40.0 nM. The fluorescein-AuNP sensor shows absolutely high selectivity toward SCN(-) than other 16 anions. The common metal ions, amino acids and sugars have no obvious interference effects. The accuracy and precision were evaluated based on the recovery experiments. The cost effective sensing system is successfully applied for the determination of SCN(-) in milk products and saliva samples.


Assuntos
Transferência Ressonante de Energia de Fluorescência/métodos , Ouro/química , Nanopartículas Metálicas/química , Leite/química , Saliva/química , Tiocianatos/análise , Animais , Bovinos , Fluoresceína/química , Corantes Fluorescentes/química , Humanos , Concentração de Íons de Hidrogênio , Limite de Detecção
14.
Acta Chim Slov ; 61(1): 73-9, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24664329

RESUMO

Sensitive and selective fluorescent probe of thiols with lower limit of detection based on fluorescence resonance energy transfer (FRET) between fluorescein and Au nanoparticles (AuNPs) is presented. The fluorescein-AuNPs complex emits weak fluorescence. Upon chemically binding to organosulfur compound that contains a carbon-bonded sulfhydryl (-C-SH or R-SH) thiols, a stable enhancement of fluorescence is observed due to the competitive binding on AuNPs between thiols and fluorescein. The magnitude of fluorescence enhancement is linearly proportional to the logarithm of the thiols concentration. We use cysteine as an example to show how this useful analytical assay works selectively, which is closely nonresponsive to 20 other amino acids even though they are in solution at a concentration 10 times greater than the thiols. The detection limit for cysteine is 7.27 × 10-9 mol L-1. The possible mechanism of this assay is discussed in details. The proposed method was successfully applied for the determination of Cys in urine.


Assuntos
Fluoresceína/química , Transferência Ressonante de Energia de Fluorescência , Corantes Fluorescentes/química , Ouro/química , Nanopartículas Metálicas/química , Compostos de Sulfidrila/química , Adulto , Cisteína/química , Cisteína/urina , Feminino , Humanos
15.
Artigo em Inglês | MEDLINE | ID: mdl-23542496

RESUMO

A new compound, 2-boronobenzaldehyde-(2'-hydroxyl-4'-sulfonic acid) naphthalene hydrazone (1), was synthesized and its structure was characterized by proton nuclear magnetic resonance, mass and element analyses. The presence of Pb(2+) led 1 to undergo colorimetric and fluorescent changes, which were detectable with the naked eye. Thus, a dual spectral response for Pb(2+) detection was introduced. In KH2PO4-NaOH buffer aqueous solution (pH 6.0), 1 exhibited fluorescence enhancement at 568 nm and hyperchromicity at 595 nm upon the addition of Pb(2+). The fluorescent intensity change was proportionate to the concentration of Pb(2+) with a dynamic working range of 5.0×10(-7) mol L(-1) to 1.0×10(-4) mol L(-1) and a detection limit of 3.7×10(-8) mol L(-1). The fluorometric method was successfully applied for the detection of Pb(2+) water of Qianhu Lake and soil in Nanchang university campus. The recoveries were 111-116% for water and 97.6% for soil respectively, determined via the standard addition method.


Assuntos
Corantes Fluorescentes/química , Hidrazonas/química , Chumbo/análise , Naftalenos/química , Cátions Bivalentes/análise , Colorimetria/métodos , Limite de Detecção , Espectrometria de Fluorescência/métodos
16.
Artigo em Inglês | MEDLINE | ID: mdl-21439896

RESUMO

A new compound, 2,5-di-[2-(4-hydroxy-phenyl)ethylene]-terephthalonitrile (DHPEPN), was synthesized. The interaction between bovine serum albumin (BSA) and DHPEPN in Tris-HCl buffer solution (pH 7.4) was investigated using fluorescence and UV-vis absorption spectroscopy. The mechanism of BSA fluorescence quenched by DHPEPN is discussed according to the Stern-Volmer equation. The binding constant and the thermodynamic parameters ΔH, ΔS, ΔG at different temperatures were calculated. The results indicate that the van der Waals interaction and hydrogen bonding play major roles in the binding process. The distance between BSA and DHPEPN is estimated to be 3.59 nm based on the Förster resonance energy transfer theory. The spectral changes of synchronous fluorescence and three-dimensional fluorescence suggest that both of the microenvironment of DHPEPN and the conformation of BSA are changed during binding between DHPEPN and BSA.


Assuntos
Nitrilos/metabolismo , Ácidos Ftálicos/metabolismo , Soroalbumina Bovina/metabolismo , Espectrometria de Fluorescência/métodos , Animais , Sítios de Ligação , Bovinos , Transferência de Energia , Cinética , Nitrilos/química , Ácidos Ftálicos/química , Solventes , Espectrofotometria Ultravioleta , Termodinâmica , Titulometria
17.
J Fluoresc ; 20(1): 243-50, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19789964

RESUMO

Water-soluble Mn(2+)-doped ZnS quantum dots (QDs) were prepared using mercaptoacetic acid as the stabilizer. The optical properties and structure features were characterized by X-Ray, absorption spectrum, IR spectrum and fluorescence spectrum. In pH 7.8 Tris-HCl buffer, the QDs emitted strong fluorescence peaked at 590 nm with excitation wavelength at 300 nm. The presence of sulfide anion resulted in the quenching of fluorescence and the intensity decrease was proportional to the S(2-) concentration. The linear range was from 2.5 x 10(-6) to 3.8 x 10(-5) mol L(-1) with detection limit as 1.5 x 10(-7) mol L(-1). Most anions such as F(-), Cl(-), Br(-), I(-), CH(3)CO(2) (-), ClO(4) (-), CO(3) (2-), NO(2) (-), NO(3) (-), S(2)O(3) (2-), SO(3) (2-) and SO(4) (2-) did not interfere with the determination. Thus a highly selective assay was proposed and applied to the determination of S(2-) in discharged water with the recovery of ca. 103%.


Assuntos
Manganês/química , Pontos Quânticos , Sulfetos/análise , Sulfetos/química , Compostos de Zinco/química , Tampões (Química) , Concentração de Íons de Hidrogênio , Tamanho da Partícula , Solubilidade , Espectrometria de Fluorescência , Espectroscopia de Infravermelho com Transformada de Fourier , Tioglicolatos/química , Água/química , Difração de Raios X
18.
J Phys Chem B ; 112(23): 7071-9, 2008 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-18489144

RESUMO

We report here that N-anilino-N'-phenythioureas in general function as a new family of thiourea-based efficient anion receptors superior to classical N-alkyl(aryl)thioureas, when the N-anilino-NH proton is acidic enough; that is, the N-phenyl substituent is not less electron-withdrawing than m-Cl. Changes due to anion binding in the absorption spectra of these N-anilinothioureas are much more substantial than those of N-alkyl(aryl)thioureas, and anion binding constants in MeCN, at 10(6)-10(7) mol(-1) L order of magnitude for AcO(-) for example, are much higher despite a similar acidity of the thioureido-NH protons. Crystal structure and (1)H NMR data show that the N-aniline chromophore is electronically decoupled from the thiourea anion binding site by the N-N bond, and an intramolecular hydrogen bond exists in MeCN but not in DMSO between the N-anilino-NH nitrogen atom and the other thioureido-NH proton. Conformation changes in the N-anilinothioureas upon anion binding were assumed to occur and lead to a much higher increment in the electron-donating ability in the N-aniline chromophore that the charge transfer (CT) is enhanced or switched on, compared to not switching on a CT in the case of N-phenylthioureas. The anion binding constant shows a stronger dependence on the N-phenyl substituent than on the N'-phenyl substituent, opposite to that observed with N-benzamidothioureas, and the CT band position of the anion binding complex depends much more on the N-phenyl substituent than that of the anion binding complexes of N-benzamidothioureas. The implications of these findings for new anion-receptors design and thiourea-based organocatalysts development are discussed.

19.
Spectrochim Acta A Mol Biomol Spectrosc ; 71(3): 814-7, 2008 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-18375177

RESUMO

A novel ditopic chromogenic receptor, N-5-(8-hydroxy)quinoline-N'-4'-nitro-phenyl thiourea (1), was synthesized. The metal complex 1-Hg(2+) showed sensitive and highly selective responses to F(-) over other anions such as CH(3)CO(2)(-), H(2)PO(4)(-), HSO(4)(-) and Cl(-). 1-Hg(2+)-F(-) complex formed, which promoted the intramolecular charge transfer and led to a dramatic spectral change. The color of 1-Hg(2+) solution changed from colorless to red upon addition of F(-). Thus, a colorimetric assay of F(-) was developed in acetonitrile by naked-eye detection. F(-) behaved linearly in the 8.0 x 10(-6) to 2.0 x 10(-5) mol L(-1) concentration range with LOD as 1.4 x 10(-6) mol L(-1).


Assuntos
Colorimetria/métodos , Fluoretos/análise , Compostos Cromogênicos/síntese química , Compostos Cromogênicos/química , Compostos de Mercúrio/síntese química , Compostos de Mercúrio/química , Estrutura Molecular , Espectrofotometria , Espectrofotometria Ultravioleta , Tioureia/análogos & derivados , Tioureia/síntese química , Tioureia/química
20.
J Fluoresc ; 18(1): 175-81, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17957452

RESUMO

In this paper we reported a metal complex 1-Zn (2,5-di-[2-(3,5-bis(2-pyridylmethyl)amine-4-hydroxy-phenyl)-ethylene]-pyrazine-Zn) as a fluorescent probe sensing DNA. The result of the competitive experiment of the probe with ethidium bromide (EB) to bind DNA, absorption spectral change and polarization change in the presence and absence of DNA revealed that interaction between the probe and DNA was via intercalation. Ionic strength experiment showed the existence of electrostatic interaction as well. Scatchard plots also confirmed the combined binding modes. The fluorescence enhancement of the probe was ascribed to highly hydrophobic environment when it bound the macromolecules such as DNA, RNA or denatured DNA. The binding constant between the probe and DNA was estimated as 3.13 x 10(7) mol(-1) L. The emission intensity increase was proportional to the concentration of DNA. Based on this, the probe was used to determine the concentration of calf thymus DNA (ct-DNA). The corresponding linear response ranged from 2.50 x 10(-7) to 4.75 x 10(-6) mol L(-1), and detection limit was 1.93 x 10(-8) mol L(-1) for ct-DNA.


Assuntos
DNA/metabolismo , Corantes Fluorescentes/metabolismo , Compostos Organometálicos/metabolismo , Animais , Bovinos , DNA/análise , Etídio/química , Etídio/metabolismo , Fluorescência , Corantes Fluorescentes/química , Compostos Organometálicos/química , Espectrometria de Fluorescência
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA